This invention relates to location detection devices for monitoring the position of a surface such as a travelling continuous or discontinuous surface. The particular embodiment to be described is for detecting variations in the thickness of biscuits passing along a conveyor.
Systems already known in which contact with a surface is required comprise mechanical gauging by means of wheels, shoes, etc. which are in regular use; while non-contact-making systems in experimental use comprise the electrical capacitance system of Wayne Kerr; the air-jet system of Clayton-Mercer used in steel making; and the new and expensive American Antech system using the laser.
It is also known to project a light beam at an angle on to a surface and to observe the movement of the position of the light spot so formed along the surface due to variation in level and to derive information therefrom.
This technique does not require contact with the surfaces to be examined, and is particularly applicable to use with moving sheets and articles during manufacturing processes.
It can, of course, be used in relation to surfaces in any position from horizontal to vertical; stationary or moving; and for any purpose in which either presence or absence; varying level; or varying thickness is to be monitored.
The present invention is an improvement in this technique utilising a photodiode array as a sequential detector.